As a successful animal group, dinosaurs appeared 240 million to 230 million years ago and ruled the world for 65.438+74 billion years until a huge asteroid hit the earth about 66 million years ago. During this period, dinosaurs evolved from a group of creatures the size of dogs or horses to the largest animals that ever existed on land.
Over time, some carnivorous dinosaurs shrank in size and evolved into birds. So from this point of view, only non-bird dinosaurs became extinct. (In this article, "dinosaur" refers to non-bird dinosaurs, unless otherwise specified. )
Great changes have taken place in the world during the 654.38+74 billion years when dinosaurs existed. Dinosaurs first appeared in Triassic (25190,000 years ago to193,000 years ago), and they roamed the supercontinent Pangea. But when the asteroid hit the earth at the end of Cretaceous (65.438+0.45 billion to 66 million years ago), the position of the continent was roughly the same as today.
The oldest dinosaur fossils can be traced back to 2,365,438+0,000 years ago, from Iski Guaras Provincial Park to the northwest of Argentina, including Herrera Dragon and Hydreau meeus Dragon.
According to the research of dinosaur scientists on the growth rate of dinosaurs, it is found that dinosaurs are probably warm-blooded animals. At first, dinosaurs were not as diverse as their crocodile-like ancestors. In fact, dinosaurs did not have absolute dominance as soon as they appeared. Ancestors like crocodiles ruled the Triassic. With the extinction of Zulong at the end of Triassic, dinosaurs survived and took over everything on the earth.
The word "dinosaur" means "terrible lizard" in Greek, which was created by British paleontologist richard owen in 1842. According to the data of Paleontology Database, as of 20021year, there were 1545 dinosaur species recorded scientifically. About 50 previously unknown dinosaur species are recorded every year, which means that there is about one newly discovered dinosaur species every week.
All these dinosaurs belong to three groups: ornithopoda, sauropoda and theropoda.
Birds and hip dinosaurs include beaked herbivorous dinosaurs, such as stegosaurus and hadrosaurs. And horned dinosaurs such as Triceratops and Ankylosaurus. Some people walk on four legs, while others walk on two legs.
Sauropod dinosaur is a dinosaur with a long neck and a big belly. Their heads are small and their limbs are columnar. This group includes sauropods, such as Liang Long. They are one of the largest land animals that ever existed on the earth.
Theropods are a group of carnivorous dinosaurs, but with the passage of time, some of them changed their eating habits and became herbivorous or omnivorous dinosaurs. Theropod dinosaurs include Tyrannosaurus Rex and Raptors, as well as bird dinosaurs. Bird dinosaurs evolved from small theropods.
So, how are these groups connected? This is debatable. The pubic bone of the flapping wing machine butt points backwards, so it is called flapping wing machine. However, they are not the ancestors of birds, but theropods. At the same time, the hips of theropods and sauropods are very similar to those of reptiles. Modern crocodiles and lizards also have this kind of ass, which is mentioned in the book rediscovery of dinosaurs.
Historically, it was thought that theropod dinosaurs were more closely related to sauropods and hip reptiles than theropod dinosaurs. However, Life Science previously reported that a study published in the journal Nature in 20 17, based on the analysis of 74 species of dinosaurs, believed that the relationship between ornithopods and theropods was closer.
Dinosaurs lived for most of the Mesozoic era, which lasted from 252 million years ago to 66 million years ago. Mesozoic includes Triassic, Jurassic and Cretaceous.
Dinosaurs evolved from the ancestors of small dinosaurs in Triassic period. At that time, the climate was harsh and dry. Dinosaurs faced competition from crocodile-like ancestors for tens of millions of years, and finally gained the upper hand when Pangea began to split. At that time, volcanoes erupted along cracks in the mainland, leading to global warming and mass extinction of ancestors.
During the Jurassic period (1.1300 million years ago to145 million years ago), dinosaurs gradually occupied a dominant position. Some dinosaurs were very big. For example, the earliest Titan can be traced back to 65438+600 million years ago. It weighs about 15 tons and is more than 15 meters long. The iconic dinosaurs of this period include Lei Long, Brachiosaurus, Liang Long and Stegosaurus.
During the Cretaceous period, with the distance between continents getting farther and farther, the dominance of dinosaurs continued to exist. The famous dinosaurs in this period are Tyrannosaurus Rex, Triceratops, Spinosaurus and Raptors. The largest dinosaurs on record, including the Argentinean dragon, can also be traced back to the Cretaceous period. The Cretaceous ended in the Cretaceous-Tertiary (K-Pg) extinction event, when an asteroid with a width of 6 miles (10 km) collided with the Earth, leaving a crater with a diameter exceeding 1 10 mile (180 km) in Yucatan Peninsula, Mexico. This impact area is called chicxulub crater.
Some dinosaurs were very big, but others were very small. The smallest dinosaur recorded is the existing bird dinosaur: the hummingbird from Cuba, which is a little more than 5 cm long and weighs less than 2 grams. According to a study in Nature magazine 20 19, the smallest extinct non-bird dinosaur is a bat-like dinosaur from China, which is 32 cm long and weighs about 306 grams.
According to a study published at the annual meeting of the Society of Vertebrate Paleontology in 20021,the longest dinosaur may be Jurassic sauropods, at least 39 meters long, and the longest may even reach 42 meters. Another competitor of the longest dinosaur is Liang Long. According to the research of the Museum of Natural History and Science in New Mexico in 2006, it is a slender Jurassic sauropod dinosaur with a body length of 33 meters.
The tallest dinosaur may be the long-necked dinosaur, which is a sauropod dinosaur with a height of 12 meter. It lived in the late Jurassic about10.5 billion years ago and lived in Tanzania today.
Many magical animals lived in the age of dinosaurs. People often confuse these animals with dinosaurs. The most common mistake is to treat pterosaurs as dinosaurs. Pterosaur is a reptile with wings, which means it can be regarded as a relative of dinosaur, but it is not a dinosaur. Crocodiles include extinct and existing crocodiles and their close relatives. Crocodiles' ancestors did not belong to dinosaurs.
In addition, the Mesozoic ocean was full of marine life, including predatory reptiles, such as black dragon, plesiosaur and ichthyosaur. However, these reptiles are not dinosaurs.